The present invention relates to a light sensitive detector arrangement having a plurality of photosensitive detector elements, the detector elements having a multilayer structure of alternating positively and negatively doped photosensitive semiconductor material with a super lattice structure and control electrodes arranged vertically and bordering on them on the front faces, to which a control voltage can be applied in order to control the spectral light sensitivity.
Such light sensitive detector arrangements frequently use gallium arsenide doped superlattices, which are arranged on a semi-insulating gallium arsenide substrate, use silicon for the n-doping and beryllium for the p-doping. The electrodes bordering on the discrete layers have n+ and p+ regions. The turnover bias voltage applied to these electrodes effects a predetermined spectral range, which fluctuates as a function of the magnitude of the control voltage.
Known image recording systems with color and black-and-white photo sensors have vidicon tubes or silicon CCD arrays, with the latter, as a rule, having photo elements arranged in rows and columns, the signal contents of which are supplied to charge-coupled arrangements.
Known black-and-white image sensors have the disadvantage that their spectral sensitivity is predetermined by the detector material used. Changing the spectral sensitivity is, as a rule, only possible by series connecting optical filters. If the spectral sensitivity of an electronic image recording system is to be changed rapidly, then, as a rule, a rapid filter change is necessary. To do this, mechanical parts are required, which swing the not-required filters out of the way and the required filter in front of the light sensitive converter arrangement. Such mechanical parts, due to the expenditures and degradation in response, are disadvantageous. Several image sensor systems are known, which comprise a plurality of photosensitive detector elements. Each array of such light sensitive detector element has a predetermined spectral characteristic. If the spectral characteristic is to be changed, an array of the photo sensitive detector elements is to be replaced by a second array with an appropriately different spectral characteristic. It is conceivable that different spectral filters are used in order to generate different spectral characteristics. Such systems, which are realized in semiconductor technology as well as also in tube technology, due to their high cost and elaboration, are disadvantageous.
Light sensitive detector arrangements are known, in which a single image sensor is used, with which a color strip filter is connected in series with, for example, red sensitivity, blue sensitivity, and green sensitivity. The discrete filter ranges alternate with each other and have, in each instance, the size of a photosensitive detector element (pixel). In this connection, there are color strip image dissectors (color stripe vidicon) and color strip CCD arrays. To each CCD photosensitive pixel in such color strip CCD arrays corresponds a color filter, which is preferentially applied on the CCD pixel.
Such semiconductor CCD arrays with series connected filters have the disadvantage that for each picture element (pixel) on the semiconductor chip, a very thin color filter, the thickness of which is approximately 10 um and having the required absorption coefficient and spectral response, must be applied. Such color filter techniques require a heat-stable and non-aging application of this filter strip on the CCD array. The danger exists that errors and fluctuations can occur regarding temperature and long-term stability of these filter layers. In addition, problems regarding the highest absorption and transmission with respect to the very thin color filter layer can arise. A light sensitive detector arrangement of the above mentioned kind is known from the literature Applied Physics A 37, 1985, pages 47 to 56, but this reference does not suggest creating largely separated spectral sensitivity ranges for electronic color image recording technology.